The s in X60s means "slim". This is achieved by the low-voltage CPU, which requires less cooling. Sellers claim an amazing 8 hour battery life.

A tiny "Radio Frequency Kill Switch" is rather hidden below the front edge of the keyboard, it stops Wireless, Bluetooth and GSM/UMTS.

Batteries

The x60s uses lithium-ion batteries in various shapes and sizes.

All these batteries apart from the ultrabay battery that fits in the base are 14.4V

It can use batteries which work with the x60, but these are approximately 3cm shorter, and leave a gap, which needs to be filled with a spacer, 92P1227/42W3050 (same part). The x61s is similar, but only some batteries are recommended.

Firstly, there are the prismatic batteries that fit flat with the bottom of the laptop - these give you a nice smooth back to the laptop and are slightly lighter in weight.

* Battery 4-cell Li-Ion (Prismatic)
o Sanyo 92P1163
o LGC 42T5224

LG Chemical 92P1165

The 4-cell cylindrical battery is slightly larger - it protrudes a little from the underside of the laptop - approximately 10mm, but is flush with the back.

The 8 cell battery is similar to the 4 cell battery, but it has an extra 4 cells in a 'bar' that goes along the entire width of the laptop, making the laptop about 20mm deeper. It's of course heavier too.